GRADLE-2034 - handle missing artifacts in mavenLocal cache.

Implement a new MavenLocalResolver which checks for artifact
existance in the maven cache before resolving the artifact
from the cache. This is to work around the issue on
systems that are using Gradle and Maven where Maven
builds will resolve an artifact POM but not the artifact
itself.
Merge branch 'gradle-2034' of https://github.com/johnrengelman/gradle
GRADLE-2034: Adapt to changed constructor signature.
GRADLE-2034: Reusing code from the parent class.